Oil wells are created by drilling a hole into the earth, in some cases using a drilling rig that rotates a drill string (e.g., drill pipe) having a drill bit attached thereto. In other cases, the drilling rig does not rotate the drill bit. For example, the drill bit can be rotated down-hole. The drill bit, aided by the weight of pipes (e.g., drill collars) cuts into rock within the earth. Drilling fluid (e.g., mud) is pumped into the drill pipe and exits at the drill bit. The drilling fluid may be used to cool the bit, lift rock cuttings to the surface, at least partially prevent destabilization of the rock in the wellbore, and/or at least partially overcome the pressure of fluids inside the rock so that the fluids do not enter the wellbore. Other equipment can also be used for evaluating formations, fluids, production, other operations, and so forth.